Which forager type would typically get the best balance of nutrients from their food?
Animal foragers
Carnivore foraging
- Carnivore prey items contain essentially the same mix of nutrients
- unlike herbivore and omnivores
- Foraging success is assumed to be limited by prey availability (quantity)
- Rather than nutritional balance (quality).
Carnivore Foraging: Quanitity vs Quality
- Food quantity driving consumption rates, and thus predator-prey populations, is often challenged
- Lotka Voltera vs Optimal Foraging
Case study #1: Wolf spiders, prey quality and consumption
- Wolf spider feeds near standing water in California (Greenstone 1979)
- 80% of the diet is shore flies, water boatmen and mosquitoes
- Prey species were marked as either present or absent in each spider gut
- spiders classified into groups (answer Q1)
- Spider stomach contents (total N = 1226) from 13 different pools of water
- Spiders from 7 out of 13 pools were more likley than by chance to have consumed all 3 prey
- polyphagy
- Side note: Can you imagine making graphs without modern computers!!!
Leveling up with Mayntz et al. 2005
- Hypothesis: IF wolf spiders optimize nutrient intake, THEN they should choose a prey type that remedies a prior nutritional deficiency
- experiment manipulating findings from Greenwood (1979)
- Nutritional state of the Wolf spiders manipulated by feeding them a pre-treatment diet
- fruit flies with high or low ratio of protein to lipid for 1-2 days.
- Then tested feeding responses to the pre-treatment food and/or a complementary alternative
- offered only 1 choice (same or different prey)
- recorded how much of each was eaten
- Answer Question 3
Leveling up with Mayntz et al. 2005 (answer Questsion 4)
Today Quantitative Reasoning Practice
- In your groups, work through interpretation of the results from these papers
- Use your knowledge of species interactions and evolution to theorize about more complex predator-prey relationships
- These are great practice exam questions!!!